Process of copper coating stainless steel



July 20, 1948. H. w. TRENBATH 2,445,372

' PROCESS OF COPPER COATING STAINLESS swam.

Filed April 26, 1945 /7' a FIEJL 1/ if INVENTOR.

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through the pipes.

0. depending portion which are provided with registering holes for the reception and retention and out of the tank, and a pair of sink rollers G and H, which are immersed in the solution B, and are mounted as shown in the oppositesides of the tank. guide the stock being coated through the pipes D. The rollers Gand H obvio ly are composed of a material which is inert to the solution B, such as hard rubber, for example.

The equipment shown in the drawings is adapted to handle a multiplicity of strands of the stock being plated, which strands are indicated by the reference number I. These strands are wire that has been partially drawn to gauge and is being coated with copper as to serve as lubricant in, further passes through drawing dies; or the stock may be finished wire whichis to be covered by a rubbercomposltion. I

In accordancewlth the specific and preferred aspects of the present invention, the strands I that are being coated are composed of stainless steel, for example that grade of stainless steel containing 18 per cent chromium and 8 per cent nickel, although the invention is not limited necessarily to the coating of such alloys, the invention being'applicable generally to the coating of any steels containing chromium or chromium and nickel in alloying amounts, 1. e., in purposely added amount-s asdistinguished from incidental traces. Where the, strands I are composed of stainless steel, and the coating metal is to be copper, the pipes D may be composed of plain carbon steel, and the solution B is a solution of a watersoluble copper salt, for instance, copper sulphate, or copper nitrate, or copper acetate, the solution being preferably acidified by addition of the corresponding acid. The pipes D preferably are perforated, as indicated by holes 9. in order to permit full access of the solution into the interior of the pipes, and free circulation of the solution The pipes D also are pro.- vided with registering holes for the introduction and retention of pin ll, which also may be of plain carbon steel, and which are slightly staggered so that opposite surfaces of the strands I come into wiping engagement with the pins ll.

and form therewith the electrolytic couple which is an important feature of the present invention.

As the strands I move through the pipes D, and contact with the pins II in wiping engagement therewith, the strands become coated,with an adherent deposit of copper, the plain carbon steel of the pipes D and pins ii dissolving as the coating proceeds, a molecule of copper being deposited on the strands 1 for each molecule of iron that enters the solution from the plain carbon steel.

The tank A may be composed of wood which has been treated to withstand corrosive action of the electrolyte B. Guide rollers E and F are mounted in brackets It by means of shaft members It, the .brackets II being secured suitably to the top of the tank. Such rolls E and F have shaft portions I? mounted in suitable bearings formed in opposite sides of the tank. as indicated in Figure l.

While the invention has been described in connection with its preferred specific embodiment, that is, coating stainless steel with copper by making the stainless steel one element of an electrolytlc couple, employing mild, or plain carbon steel as the other element of the couple with copper sulphate as the electrolyte, in its broader aspects the invention provides a method of coating alloy steels containing chromium, or chromium and nickel, in alloying quantities,with a coating metal by immersing the steel to be coated in an aqueous solution of a water-soluble compound of the coating metal as electrolyte, and maintaining the immersed alloy steel in contact with a metal electropositive to the coating metal, thereby producing a galvanic electrolytic couple between the alloy steel and the. electropositive metal, thereby producing a plating of the coating metal on the the perforated ipes D and inserted pins ii, any

other contact bodies may be employed that may be convenient, so long as such bodies are composed of a suitable electroposltive metal. Thus, in the embodiment of the invention herein speclfically described and illustrated, there may be employed as contact bodies. dragging chains of plain carbon steel, or multiple contact sinkers of plain carbon steel, such bodies functioning as well as the illustrated perforated pipe and inserted pins. a

In practice, the temperature of the bath is maintained, in any suitable manner, between F. and F. Any water-soluble copper salt may be employed, such as cupric sulphate, cupric acetate. cupric nitrate, and the like; or a mixture of copper salts may be employed. such as a com-. position approximating 78 per cent cupric sulphate, approximately 20 per cent cuprous chloride, and approximately 2 per cent of an addition agent such as a lignin composition ("goulac), or other well-known addition agents. It will be understood that the aforementioned bath compositions are not critical nor even illustrative of the only operative copper coating baths, a bath composed simply of a solution of copper sulphate functioning substantially equally as well. The bath can be employed by keeping up the proper percentage of acidity until a, Baum gravity of 20 is reached. In practice, the following sizes of wire have been coated successfully by the process of the present invention, at the indicated maximum speeds, this data being given by way of iilustrative examples of the present process:

1; inch diameter wire (0.312 in), 34 feet per minute ,8-gaug (Washburn and Moen gauge), diameter 0.162 inch, 47 ft. per minute 13 gauge (Washburn and Moen gauge), diameter 0.0915 inch, 61 ft. per minute very slowly as no iron'is taken from the stainless wire that is run through the bath. As has been indicated above, the solution can be used by keephis the proper percentage of acidity until a Baum gravity of twenty degrees is reached.

I cl:

The process of electrochemically coating stainless steel wire with copper without externally applied electric current, which comprises moving the stainless steel Wire through an aqueous solution of copper sulphate as electrolyte and maintaining the wire while immersed in said solution in contact with plain carbon steel bodies, 'the'stainless steel wire and plain carbon steel bodies being in direct contact with each other at spaced apart points within said solution, thereby for-mint, at galvanic couple between the stainless steel wire soul the plain carbon steel bodies, said contact be- 6 v V in: maintained until said wire copper from the electrolyte.

HERBERT W. TRENBATH. nnmlmnoes crrl-m The following references are of record in the file of this patent:

UNITED s'm'ms PATENTS Kennedyet el Nov. 2t, 1944 is coated with 

